In semiconductor manufacture apparatuses, there are a film forming apparatus and an etching apparatus in which a gas supply device is positioned to face a loading board in a processing chamber and supplies a process gas from the gas supply device to a substrate (for example, a semiconductor wafer, hereinafter called “a wafer”) mounted on the loading board to process the substrate.
As for the film forming apparatus, there is a thermal CVD apparatus that heats and reacts the process gas. Also, there is known a process so called ALD (Atomic Layer Deposition) or MLD (Molecular Layer Deposition) in which the supply of a plurality of the process gas is divided into two processes (step), and a first process gas is supplied in a first process and a second process gas is supplied in a second process thereby performing each of the first and second processes alternately and laminating the reaction product of the process gas in order. See, for example, paragraph [0002] of Japanese Patent Laid-Open Publication No. 2004-91874. Regarding ALD, there is known a side flow type that the process gas is forced to flow along the side surface of the wafer. However, the present inventor believes that it is advantageous to supply the gas from a direction that faces the wafer in ALD as well.
Among the gas supply devices, there is a type called a gas shower head. In the lowest part of the gas shower head, a gas supply plate, called a shower plate formed with a plurality of gas supply holes, is formed. And, the gas shower head includes a gas input port and a gas flow path for linking the gas input port to the corresponding gas supply hole, and a diffusion space is formed in the gas flow path for diffusing the gas in a horizontal direction.
When converting the process gas in ALD, a purge gas is supplied before the supply of the next process gas begins. Thus, the process gas remained in the processing atmosphere is eliminated completely. The purge process is an important process that prevents the occurrence of the particles. In case there is insufficient purge process, for example, when two kinds of the process gases are passed and flowed through a common gas flow path or diffusion space, the process gases remained in the process atmosphere or in the gas supply device and newly supplied process gas react each other so that the reaction product is adhered to the wall. This is a reason that the particles are generated. Also, when each process gas is supplied by passing through each of the flow path in the gas shower head, because of the inverse-diffusion toward the inside of the gas supply hole, the process gas of one side penetrates into the flow path of the other side and reacts with the process gas of the other side where the purge process is not completed thereby adhering the reaction product. Meanwhile, the purge process is a subsidiary process that does not directly contribute to the film forming. On this account, it is desirable that the duration time of the purge process is as short as possible to improve the yield and the process gas can be completely flush out in this short time of the purge process.
In this point, the gas shower head needs comparatively large diffusion space to supply the process gas regularly to each of a plurality of the gas supply hole formed on the front surface of the shower plate, therefore the process needs time for substituting the inside of the diffusion space with the purge gas. Also, the gas tends to be filled in the corner of the diffusion space during the purge process. These are obstacles in eliminating the process gas completely.
Also, from the manufacturing point of view of the gas supply device, for example, a precise process is necessary because the gas shower head requires a plurality of fine hoes in the plurality of plates, and the plates are stacked together to form the gas flow path. Thus, it is not an easy process to manufacture the gas shower head and the manufacturing cost is relatively high.
The present inventor considered the gas supply nozzle having the same appearance as the gas supply nozzle used in an etching apparatus disclosed in Japanese Patent Application Laid-Open No. 2007-243138 (specifically, Claim 1, [0003], FIG. 1), as the gas supply device in ALD.
For example, as illustrated in the film forming apparatus 100 of FIG. 22A, gas supply nozzle 41 is formed by projecting into a process space, and a plurality of gas supply holes are formed on the surface of the gas supply nozzle. Also, since gas supply nozzle 41 is very small and has a simple constitution, the purge process may be performed within a short time. Also, it is easier to manufacture the gas supply nozzle 41 than the gas shower head.
However, when gas supply nozzle 41 is projected from the ceiling of the processing chamber, even if the wafer W is positioned as close as possible to gas supply nozzle 41, at least the ceiling has to be apart from the wafer W with the height of gas supply nozzle 41. For this reason, there is a concern that the purge time may take too long because the volume of process atmosphere 10 becomes relatively large. Also, if the volume of process atmosphere 10 gets large, there is concern that the cost of the film forming process may be increased because the necessary amount of process gas becomes large to maintain process atmosphere 10 with a required concentration of the process gas.
Thus, as illustrated in FIG. 22B, the present inventor developed a film forming apparatus 101 in which the lower space of the loading board is separated from process atmosphere 10 and the process gas is exhausted to the side thereby reducing the space necessary for the purge process. However, the film forming apparatus has some problem in that the exhausted gas tend to hit the side wall of the processing chamber 2 and generate a vortex of air current prohibiting a complete exhaustion of the process gas from the processing chamber.
In Japanese Patent Application Laid Open No. 2005-507030 (specifically, [0020], [0021], FIG. 3), an ALD type film forming apparatus is described formed with a taper surface at the ceiling of the processing chamber. The taper surface is formed on this apparatus in order to supply the process gas uniformly in a substrate surface. Also, the process gas is supplied into the processing chamber through the gas flow path which is an opening formed at the peak portion of the processing chamber. However, the constitution of the apparatus is basically different from the constitution described above in which the gas supply nozzle is projected from the ceiling of the processing chamber.